1. Field of the Invention
The present invention relates to a structure and method of forming a semiconductor material wafer and, more particularly, to a structure and method of forming the wafer with sacrificial layers.
2. Description of the Prior Art
The Czochralski technique for growing single crystals is named CZ seed-pulling (1918). Silicon wafers are generally taken from crystals grown by Teal and Buehler. The CZ dislocation-free single crystal was developed by Dash.
The CZ method comprises the following steps: (1) poly charging; (2) meltdown; (3) necking and crown; (4) body growth; and (5) tail growth.
(1) poly charging and (2) meltdown—a new crucible is charged in the Graphite suspector, and the chuck polycrystalline silicon (“polysilicon”) and dopant are charged to the crucible. In order to reduce the quartz crack caused by polysilicon and the suspector, the large diameter of chuck polysilicon is charged in the bottom and side of the suspector, and the dopant is charged in the central. The furnace is then closed, vacuumed, the leaking rate is checked, and heating is performed at a temperature higher than 1420° C. to completely melt and maintain for a time in order to uniformly mix the melted solution. If the chuck and granular material are used together, the granular material is slowly added from the side of the furnace before the chuck is completely melted, in order to achieve the desired total amount, and maintained for a time so as to evaporate the gas, in order to achieve the stable status of the solution temperature, the suspector temperature, and the thermal field.
(3) necking and crown through (5) tail growth—the temperature of the melted solution surface is fine-tuned by dipping the seed crystal into the solution, thereby monitoring the melting status. A monocrystalline seed with a specific shape and crystal orientation (1.7×1.7×2.5 cm )is dipped into the solution about 0.3 cm. If this dipped seed crystal is easily melted, the output power of the heater needs to be reduced. If the dendritic polysilicon is grown outwardly from the dipped seed crystal, the output power needs to be increased. Under proper temperature, the seed crystal is rotated and pulled. The dipped seed crystal is pulled to form a new monocrystalline seed with a diameter of 0.5˜0.7 cm. It is so-called “the neck”. The growth rate of the neck diameter and the internal quality are controlled by skilled operators. The purpose of growing the necking is to eliminate plastic deformation defects 5 caused by machining, for example, dislocation and vacancy, or defects caused by rapidly heating the seed crystal contacted with the solution.
The grown ingot is sawed into a plurality of slip wafers, thereby forming the required structures on the wafers. Since each wafer is not easy to form, cracks are inspected by instrumentation when the wafer edge or even the main body generates a crack caused by the external factors during the subsequence processing. This usually wastes resources and increases costs.